Peptidyl-glycine alpha-amidating monooxygenase is an enzyme that catalyzes the biosynthesis of many signaling peptides and, in humans, is encoded by the PAMgene.[1][2] This transformation is achieved by conversion of a prohormone to the corresponding amide (C(O)NH2). This enzyme is the only known pathway for generating peptide amides, which renders the peptide more hydrophilic.[3] The reaction pathway catalyzed by PAM is accessed via quantum tunneling and substrate preorganization.[4]
Function
This gene encodes a multifunctional protein. It has two enzymatically active domains with catalytic activities - peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL). These catalytic domains work sequentially to catalyze neuroendocrinepeptides to active alpha-amidated products. Multiple alternatively spliced transcript variants encoding different isoforms have been described for this gene, but some of their full-length sequences are not yet known.[2]
The PHM subunit effects hydroxylation of an O-terminal glycine residue:
Involving hydroxylation of a hydrocarbon by O2, this process relies on a copper cofactor. Dopamine beta-hydroxylase, also a copper-containing enzyme, effects a similar transformation.
The PAL subunit then completes the conversion, by catalyzing elimination from the hydroxylated glycine:
The eliminated coproduct is glyoxylate, written above as CH(O)CO2−.
References
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Vos MD, Jones JE, Treston AM (1995). "Human peptidylglycine alpha-amidating monooxygenase transcripts derived by alternative mRNA splicing of an unreported exon". Gene. 163 (2): 307–11. doi:10.1016/0378-1119(95)00364-C. PMID7590286.
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Yun HY, Johnson RC, Mains RE, Eipper BA (1993). "Topological switching of the COOH-terminal domain of peptidylglycine alpha-amidating monooxygenase by alternative RNA splicing". Arch. Biochem. Biophys. 301 (1): 77–84. doi:10.1006/abbi.1993.1117. PMID7680192.
Mains RE, Milgram SL, Keutmann HT, Eipper BA (1995). "The NH2-terminal proregion of peptidylglycine alpha-amidating monooxygenase facilitates the secretion of soluble proteins". Mol. Endocrinol. 9 (1): 3–13. doi:10.1210/me.9.1.3. PMID7760848.
Tateishi K, Arakawa F, Misumi Y, Treston AM, Vos M, Matsuoka Y (1995). "Isolation and functional expression of human pancreatic peptidylglycine alpha-amidating monooxygenase". Biochem. Biophys. Res. Commun. 205 (1): 282–90. doi:10.1006/bbrc.1994.2662. PMID7999037.
Martínez A, Montuenga LM, Springall DR, Treston A, Cuttitta F, Polak JM (1993). "Immunocytochemical localization of peptidylglycine alpha-amidating monooxygenase enzymes (PAM) in human endocrine pancreas". J. Histochem. Cytochem. 41 (3): 375–80. doi:10.1177/41.3.8094086. PMID8094086.
Kapuscinski M, Green M, Sinha SN, Shepherd JJ, Shulkes A (1993). "Peptide alpha-amidation activity in human plasma: relationship to gastrin processing". Clin. Endocrinol. 39 (1): 51–8. doi:10.1111/j.1365-2265.1993.tb01750.x. PMID8102327.
Yun HY, Keutmann HT, Eipper BA (1994). "Alternative splicing governs sulfation of tyrosine or oligosaccharide on peptidylglycine alpha-amidating monooxygenase". J. Biol. Chem. 269 (14): 10946–55. PMID8144680.
Ouafik LH, Mattei MG, Giraud P, Oliver C, Eipper BA, Mains RE (1994). "Localization of the gene encoding peptidylglycine alpha-amidating monooxygenase (PAM) to human chromosome 5q14-5q21". Genomics. 18 (2): 319–21. doi:10.1006/geno.1993.1471. PMID8288234.
Husten EJ, Tausk FA, Keutmann HT, Eipper BA (1993). "Use of endoproteases to identify catalytic domains, linker regions, and functional interactions in soluble peptidylglycine alpha-amidating monooxygenase". J. Biol. Chem. 268 (13): 9709–17. PMID8486658.
Yun HY, Milgram SL, Keutmann HT, Eipper BA (1996). "Phosphorylation of the cytosolic domain of peptidylglycine alpha-amidating monooxygenase". J. Biol. Chem. 270 (50): 30075–83. doi:10.1074/jbc.270.50.30075. PMID8530412.
Morris KM, Cao F, Onagi H, Altamore TM, Gamble AB, Easton CJ (1 December 2012). "Prohormone-substrate peptide sequence recognition by peptidylglycine α-amidating monooxygenase and its reflection in increased glycolate inhibitor potency". Bioorganic & Medicinal Chemistry Letters. 22 (23): 7015–7018. doi:10.1016/j.bmcl.2012.10.004. PMID23084901.